Could someone please guide me a bit on the use of TV airbags when mounting a TT on a WD hitch?

Should the airbags be deflated to just a few pounds before getting the TT/TV level by use of the WD hitch setup? And then readjusted accordingly?

Seems to me, if the airbags are left at say 50# (which does raise the stern end of my truck) this might affect the level once the TT and TV are mated together?

It's my understanding that using a WD hitch will raise the stern end of my truck somewhat, in its load transfer to the front axle more.
How then do airbags affect that weight transfer dynamic, if at all.

Thanks

 

It's a tricky combination. I always set my airbag pressure for towing, usually 40-50 and then set up my WD hitch. If you set up the WD hitch and then air up the bags you just defeated what the WD hitch was going to do for you.

 

If you inflate the bags after setting the hitch, when you inflate them you raise the rear and reduce the tension on the bars - thus reducing forward weight transfer to the front axle.

I can see this being a balancing act to get everything set the way you want.

My thinking is, if you set the bars with the bags over-inflated, then reduce the pressure in the bags, you will be increasing forward weight transfer as you reduce pressure. This might make it easier to find a pressure you like. IDK ... I've never used both together.

This came up in the expedition forum a while ago. Someone was having problems with the automatic leveling rear suspension and the WDH. that system takes a couple of miles to automatically adjust ride height, and as it did it was taking weight off his front axle. About the only thing he could do was readjust after the rear suspension was pumped up...

 

Just thinking out loud here, but what if you hooked up the trailer with out attaching the bars. Air up the bags to level, then drive to a parking lot to complete the bar installation?

 

That's probably how I would approach it ....


keep in mind that the rear will be higher with the bars tensioned than without. so there is a good chance that when you get it "leveled out" without the WD Bars tightened the rear will be too high once you tighten them up.


but, as I said before, as you lower the rear by letting air out of the bags, the weight transfer to the front will increase, so you might be able to find that happy medium between the two easier than you would trying to do it the other way.


my thoughts ...

 

My Range Rover air suspension system pretty much did it this way as it always returned the vehicle to level regardless of the load in the rear. Even though it was level, you could feel the steering difference moving up or down a chain link on the WD hitch.

 

I did this for years - it's easy. Just put the air bags at the pressure that you will tow and set your hitch up. Your spring bar tension is set with the air bags inflated to tow pressure, which makes sense as you tow at the same pressure.

 

Right, but how did you establish your "towing pressure"?

Randomly before you hooked up, or after you set your bars up?

I think that's the crux of the problem. I know on my rig, the difference in rear suspension height with and without the bars is in the 3"-4" range. And it is about 2"-3" lower than unloaded even with the bars hooked up.

As the rear comes up, the bars unload.

 

This is the process I used setting up my truck. I have done no suspension work except for adding the air bags.

1. Level the trailer to set hitch height.
2. With no air in the air bags adjust hitch height to match trailer coupler.
3. Connect trailer and Add air to air bags till trailer is level. This sets the air pressure for towing. On mine I'm right at 55 lbs.
4. Install and adjust equalizer bars. I have a Reese hitch with 1000 lbs round bars in the 3rd link and this gives me 1/2 loading on the front end measured at the front bumper. My truck handles great with a very stable ride.

 

that may work well for larger vehicles like yours, but I can see how only getting 50% of the front axle weight back would not work for shorter or lighter tow rigs.


Air bags or no airbags, there is no way in heck you'd ever get the trailer back to level or the rear of the truck back to it's original height with my expedition.


forward weight return is first and foremost. ride height has to take a back seat to that.


I'd be willing to bet that your trailer would be too high if you were putting enough tension on the bars to get closer to 100% forward weight return.


if I had my bars set like that, I guarantee my rig would be nearly un-drivable.


if I were going to modify your procedure to work with my rig, or anything that isn't a 3/4 ton diesel, I'd do everthing the same, but set the bars for more forward weight return, then let the air down in the back to level it back out. doing it this way keeps your forward weight (actually increases it).


JMO.

 

Airbags should not be used for leveling while using a WD hitch as it defeats the design of the WD hitch. It is a balancing act and you will find varying opinions and methods, some of which might bring you out to the correct settings.


I followed Ford's instructions in the manual for setting up my WD hitch and then I use the airbags to snug up or support the rear shocks, which is about 35 to 40 lbs. Once you know the correct air bag pressure, they do not have to be aired up and down every time you hitch up as long as you have the same WD settings. A trip to the CAT scales will verify that you have transferred the desired amount of weight to the front axles of your tow vehicle and the axles of the TT. If not enough weight is on the front axle of your TV with your WD hitch, the air bag will exacerbate this and your TV will feel light in the front end and you will not have a an enjoyable tow experience particularly if you are in wet or slippery conditions.

 

Airbags should not be used for leveling while using a WD hitch as it defeats the design of the WD hitch. It is a balancing act and you will find varying opinions and methods, some of which might bring you out to the correct settings.


I followed Ford's instructions in the manual for setting up my WD hitch and then I use the airbags to snug up or support the rear shocks, which is about 35 to 40 lbs. Once you know the correct air bag pressure, they do not have to be aired up and down every time you hitch up as long as you have the same WD settings. A trip to the CAT scales will verify that you have transferred the desired amount of weight to the front axles of your tow vehicle and the axles of the TT. If not enough weight is on the front axle of your TV with your WD hitch, the air bag will exacerbate this and your TV will feel light in the front end and you will not have a an enjoyable tow experience particularly if you are in wet or slippery conditions.

 

This is not exactly correct. For trucks that experience sag under light loads, using the air bags to preload the suspension will prevent sag. You can set the rear bumper level or raked if you wish, it's really personal preference. The attitude of the truck body has no bearing whatsoever on how well it tows.
Only the distribution of weight between the axles affects how the vehicle tows. Once the body height of the truck is set, measure the height of the front bumper then attach the trailer. Measure the height of the front bumper again. The lifting of the front bumper is a physical manifestation of weight being shifted from the front axle to the rear axle. You can adjust the torsion bars of the weight distribution hitch to bring the measured height of the front bumper down to the measured height before the trailer was connected. This method will redistribute the weight between the trailer axle(s), the rear axle and the front axle of the truck.
You can verify this at the CAT scales (I have). If you are not happy with the distribution of weight between the axles, simply adjust the spring bars and re-weigh until you like the distribution.

 

I tried that method with one of my previous trucks and bent the clamps on the trailer A frame trying to get the truck level. The rig was no longer safe and I had to stop my trip home to buy a new set of clamps. That was why I went to airbags, for supporting the additional weight on the rear axle and then use the weight distribution to transfer some of the total weight to the front axle. I didn't try to return weight to the front but increased weight on the front axle and thereby keep my truck in a more normal attitude for driving.

I'm not a degreed engineer or an expert on these hitches so all I know is this works for me. I'm not going to say you're wrong but it caused me issues doing it your way. In the end you have to be comfortable with what you have and if you get there safe that's what counts

 

I follow what you are saying, but I've never recommended using the WD hitch to "level the truck". there are some vehicles where that is simply not possible. the newer super duties being one of them. an extended E250/350 being another.


the WD bars are for distributing weight, not leveling the truck. a level truck can be a byproduct of evenly distributed weight, but they are not the same thing.


I've always recommended getting the front axle weight as close to your unloaded weight as possible. barring scale weights, the best way to get that is to measure your front fender before you hook up, and then set your hitch such that the front fender height is as nearly the same as possible to the unloaded measurement, and forget completely about what the rear of the truck is doing.


now, if by doing the above you still are not level, then it is time to look at some help in the rear of the truck. airbags, timbrins, helper springs, ect.


my point was that depending on how you do it, you can end up making things worse with airbags. if you set your hitch to where it is driving good, then inflate your bags you are going to unload the front axle when you inflate the bags. when you are trying to establish your setup, you are better off setting the bars with the bags slightly over inflated, then setting the front ride height, then lowering the pressure in the bags so that you don't unload the front and have to start all over. it's a balancing act as one directly affects the other. once you have your hitch set and your pressure determined, then you are set and just use those numbers. but getting the initial set up can be a bit tricky.


concern yourself first with the amount of weight you are returning to the front axle, then concern yourself with the attitude of the tow vehicle, keeping in mind that on some vehicles there is nothing you can do.


if you are going to use both, just be aware that the amount of air you have in the bags can and will affect the amount of weight retuned to the front axle.